plan astro pro nsf nov 2003 drf [drf]
Physical Observations of Very Young Dynamical Families of
AsteroidsPRIVATE
A Proposal submitted to the NSF "Planetary Astronomy"
Program
14 November 2003
Principal Investigator:
Clark R. Chapman ([email protected])
Southwest Research Institute (SwRI)
Suite 400, 1050 Walnut St.
Boulder, CO 80302
Co-Investigators:
William J. Merline (SwRI)
David Nesvorný (SwRI)
Eliot F. Young (SwRI)
Peter Tamblyn (Binary Astronomy)
Collaborators:
Petr Pravec (Astron. Inst., Ondrejov, Czech R.)
I. INTRODUCTION
Synopsis
An extraordinary discovery by Co-I Nesvorny (Nesvorny et al.
2002, 2003) presents a stunning opportunity to address, for the
first time, some fundamental issues in planetary science, including
the rates of processes that physically affect asteroids. Here, we
propose a carefully coordinated program of astronomical
observations of members of three special families of asteroids.
Perhaps the most vital but difficult-to-obtain kind of planetary
fact is the absolute age of an event. Until now, the only precise
dates for such events were from radioisotopic dating techniques
(e.g. of moon rocks, meteorites, terrestrial rocks). However, many
such ages are compromised since we don't know where the rocks come
from -- which unit on Mars, which asteroid, etc. Therefore, most
insight about absolute chronologies of planetary bodies are from
indirect techniques, like crater-counting, which provide very crude
ages (e.g. plus-or-minus factor of 2) for the age of, say,
Ganymede's surface or the timing of an asteroid family-producing
collision. With no good absolute ages available, rates of basic
planetary processes thus remain imprecise.
The brilliant discovery of Nesvorny et al., which we propose to
exploit, is a robust, dynamical dating of the formation of two
asteroid families to a precision of only a few hundred thousand
years! They find that the Karin cluster (part of the famous Koronis
family) formed in a catastrophic collision just 5.8 ±0.2 My ago.
Also, a part of the Veritas family formed in such a collision 8.3
±0.5 Myr ago. And a third cluster, Iannini, is younger than either
of them. Not only are these ages unexpectedly recent (just ~0.2% of
the age of the solar system) but they are known with unprecedented
precision. This is the first time that robust, precise, absolute
chronological ages can be unquestionably assigned to particular
asteroids -- in this case, to members of three asteroid families.
The extraordinary opportunity that we propose to exploit is to use
these youthful age-determinations to study the rates of fundamental
asteroidal processes through a suite of astronomical observations
of these exceptionally young asteroid families. For processes that
have rates much longer than millions-of-years (e.g. orbital
evolution of asteroid satellites, evolution of asteroid spins), we
have, at last, the opportunity to study initial conditions. For
processes that have rates the order of a few million years or less
(e.g. space weathering, loss or covering of volatiles), we have a
chance to study the early rates of processes that have gone to
completion for most asteroids.
We have assembled a research team with extensive experience in
observational astronomy of small bodies including (a) noted
asteroid authority Clark Chapman (with decades of experience in
asteroid spectrophotometry and photometric geodesy, as well as a
specialist on space weathering and asteroid families); (b) asteroid
satellite expert Bill Merline (who has discovered many asteroid
satellites using adaptive optics [AO] systems on the CFHT, Keck,
VLT, Gemini, and HST telescopes); (c) small-body spectroscopist
Eliot Young (a frequent observer at IRTF and with NIRSPEC on Keck);
(d) noted lightcurve specialist Petr Pravec (our overseas
Collaborator); (e) Peter Tamblyn (a specialist in computational
astronomy and an IR spectroscopist), and (f) dynamicist David
Nesvorný (who made the remarkable theoretical/numerical discoveries
that underpin our proposed observing program). For many
representative members of the Karin and Veritas clusters (and of an
even younger group, the Iannini cluster), we propose coordinated
observations of IR spectrophotometry and radiometry (using SpeX and
MIRSI at IRTF), medium-resolution spectroscopy (using NIRSPEC at
Keck), adaptive optics imaging (using VLT and Gemini), and
lightcurve photometry (using various telescopes in Europe and the
American Southwest). Our goal is to search for both predicted and
serendipitous indications of youthfulness of these asteroids by
obtaining observations that enable us to contrast them with similar
data previously published for normal, older main belt
asteroids.
Background
The fundamental process affecting asteroids in recent aeons is
mutual catastrophic collisions. They (a) create asteroid families
(clusters of asteroids with similar orbital elements); (b) produce
the fragmental size distribution; (c) rearrange large "rubble pile"
assemblages; (d) provide the delta-v's that move fragments into
chaotic zones, which can radically change their orbits and remove
them from the asteroid belt, sometimes into Earth-approaching
paths; and (e) establish the distribution of spins, shapes, and
configurations (e.g. presence of satellites). Collisional processes
also shock, de-gas, or even melt the constituent minerals in
asteroidal rocks (meteorites).
For several decades, observations of families have critically
constrained asteroid collisional/dynamical evolution (cf. Arnold
1969; Gradie, Chapman & Williams 1979; Chapman et al. 1989; and
chapters in Sect. 5.1 in Asteroids III [Bottke et al., 2002]).
Based on incomplete analysis, some attributes of families seemed
understood, as of a few years ago: (a) Families are not numerous;
only a few dozen have been reliably established. (b) Most families
are inferred to be very old, with ages of hundreds of millions to
billions of years. (c) Families generally represent the break-up of
homogeneous precursor bodies; that is, the spectral properties
(taxonomic types) of family members are usually similar and often
distinct from background asteroids in the same region of the belt.
We have found preliminary evidence (e.g. in the Sloan Survey
[Ivezic et al. 2002]) suggesting that Karin cluster members, like
Koronis members generally, are S-types while Veritas members are
varieties of C-type (indications of greater heterogeneity among
Veritas members {DiMartino et al., 1997} may be in error, in our
opinion, based on disparities with data from Bus, 1999). Family
attributes (a) & (b) appear compatible with a developing
appreciation from hydrocode modelling of asteroid collisions (cf.
Benz & Asphaug 1999) that it is difficult to catastrophically
fragment, disrupt, and disperse large asteroids, so relatively few
families have formed in recent aeons.
This picture has recently been augmented by detailed dynamical
analysis and numerical simulations. It is now realized that
families are subject to slow spreading and ultimate dispersal due
to often-minor resonances in the belt. Moreover, smaller asteroids
are moved, over longer durations, by the Yarkovsky Effect (due to
asymmetric absorption and re-radiation of sunlight), further
dispersing families. Therefore, instead of family dimensions and
shapes directly reflecting the immediate outcomes of cratering
events or catastrophic disruptions, they reflect this dynamical
diffusion, often etched by chaotic zones at the borders of, or even
within, the families. Therefore, it is vital to find a young,
just-formed family in order to compare with predicted outcomes of
hydrocode simulations of collisions.
Now, one of us (Nesvorný) has led research yielding an
unexpected, startling, but robust result (Nesvorný et al. 2002): a
portion of the Koronis family -- one of the large families
identified by Hirayama nearly a century ago -- is apparently the
product of a disrupted moderate-sized (~25 km diameter) Koronis
family member only 5.8 ±0.2 My ago (< 0.2% the age of the solar
system, "yesterday" in relative cosmic terms). (Fig. 1 shows a
simulation of such a break-up.) The largest member of this cluster
of 75 asteroids (up from 39 known a year ago) is 832 Karin, so we
call it the Karin cluster. It is not wholly unexpected that at
least one family might be as young as only 5.8 My because the
expected frequency of disruption of 25 km asteroids (the rough
diameter of the Karin cluster precursor) suggests that the most
recent disruption would have occurred ~10 My ago. Remarkably, we
have not only identified the family but have precisely dated the
event! So we now know we have a nearly pristine family, a
"snapshot" in the immediate post-collision phase, before dynamical
diffusion has progressed far at all.
Now we can undertake all kinds of potential tests for
time-dependent asteroidal phenomena and behavior, which should have
evolved little since the family formed. We propose a suite of
observations to determine specific characteristics (e.g. lightcurve
periods, presence of volatiles, radiometric fluxes) of Karin
cluster members. Unexpected attributes of very young asteroids
might also be revealed. Among the phenomena with observable
attributes or consequences that evolve or mature over time scales
of tens of thousands of years to billions of years, but which might
be incomplete after just a few million years, are: space weathering
of asteroid surfaces, tidal evolution and collisional destruction
of asteroidal satellites, sublimation of large ice pockets that may
have survived within the parent asteroid but are now at or near the
surface of disrupted fragments, and Yarkovsky dispersal of family
members. We can also study traits of members of a truly
freshly-formed family (e.g. shapes, spins, bias-corrected size
distribution) to compare with predicted outcomes of hydrocode
simulations of collisional disruption and family formation.
Very recently, Nesvorný et al. (2003a) have found that another
family (Veritas) is also extremely young, 8.3 ±0.5 My. In the same
paper, Nesvorný et al. offer a powerful dynamical argument that yet
another small cluster, associated with 4652 Iannini, is even
younger than Karin, <5 My, although in this case a precise age
determination is not possible. Thus, in addition to proposing a
suite of focused telescopic observations of a sample of Karin
cluster members, we propose similar observations of many members of
the Veritas family (which, being composed of C-types, is
complementary to the apparently S-type Karin cluster), and of the
Iannini cluster (which has 27 members, if we include the bright
object Nele, of which 19 will be brighter than V=18 sometime during
July 2004 – Dec. 2007). Since Iannini is an even younger cluster --
though its precise age isn't known -- it presents the very youngest
asteroids known! Our proposed observations will provide diagnostic
tests of issues of young-vs-old asteroid families, employing
infrared spectrophotometry (at both low- and moderate-resolution),
radiometry, adaptive optics imaging, and extensive lightcurve
photometry. The broad array of techniques that we intend to employ
may also lead to serendipitous discoveries of unexpected attributes
of exceptionally youthful asteroids. We propose to observe many of
the currently identified Karin cluster members, a large statistical
sample of Veritas members, and as many of the few Iannini cluster
members as possible -- perhaps ~100 asteroids in all (obviously
fewer for techniques restricted to brighter objects, like AO
imaging). We will usually observe brighter members to reduce
integration times, but will spend some time sampling a few faint
(V~19.5) family members at adequate S/N, to study potential
size-dependencies.
II. TECHNICAL BACKGROUND
During the 1990s, new methods of reliably identifying asteroid
families revealed a few tens of families (Zappalà et al. 1994).
Researchers look for clusters of asteroid positions in the
3-dimensional space of the so‑called proper orbital elements (which
average over the rapidly varying osculating elements): proper
semimajor axis aP, eccentricity eP, and inclination iP. Proper
elements are much more constant over time than instantaneous
orbital elements; thus a cluster in proper-element space suggests
common ancestry. In recent years, improvements in proper element
calculation and clustering algorithms have finally yielded reliable
family identifications (Milani and Kne_evi_ 1994); see Fig. 2. As
asteroid discoveries rapidly increase, family identifications have
also multiplied. Recently it has been learned that members of
families gradually drift apart in (aP,eP,iP) space (Bottke et al.
2001, Nesvorný et al. 2002b). So the youngest families are expected
to be those that are still compact.
Co-I Nesvorný et al. (2002, hereafter NBDL02) applied the
Hierarchical Clustering Method (HCM, Zappalà et al. 1994) to a new,
state‑of‑the‑art proper element database (Kne_evi_ et al. 2002,
http://hamilton.dm.unipi.it/ cgi‑bin/astdys/astibo) to search for
compact families with just 1/10th of the typical separations of
most families. They found a prominent, compact cluster of 39
asteroids (including Karin) within the Koronis family (see Fig. 3);
its orbital distribution is diagonal in (aP,eP) and fits inside the
similarly‑shaped "equivelocity" ellipse shown in Fig. 3 (cf.,
Morbidelli et al. 1995). Simulations match the ellipse if the
precursor body was near its perihelion when a catastrophic
collision and break-up occurred, launching fragments away at ~15 m
s-1. Cluster fragments then circled the sun as a group. But within
~1000 years, they drifted away from each other around their nearly
common orbits. Over longer durations, their orbital orientations
(longitude of ascending node, argument of perihelion) also drifted
apart, around 360º, due to planetary perturbations. (It is the
failure of the latter elements to fully spread in the case of the
Iannini cluster that demonstrates its extreme youth.) After only a
few million years, the once-clustered asteroids had dispersed into
a toroid around the Sun, like the IRAS dust bands (only aP,eP,iP,
remain tightly clustered for long durations). By numerically
integrating the orbits back in time to an instant when all the
orbital elements are clustered (Fig. 4), NBDL02 could find the
absolute time when the Karin cluster formed: ~5.8 My ago. (The
chance that such a convergence could happen by chance during the
full age of the solar system is <10-6!) This first-ever dated
event must not be confused with the event that created the Koronis
family. The age of the Koronis family, based on cratering studies
of Ida (a Koronis member) and collisional/dynamical evolution
studies, is 2-3 Gy (Chapman 2002, Marzari et al. 1995, Bottke et
al. 2001), more than 400 times older than the Karin-cluster event,
which is a very recent secondary disruption of an asteroid within
the Koronis family. (Indeed most asteroid families have
indirectly-inferred, low-reliability ages that are very old [cf.
Marzari et al. 1995], often billions of years.)
A similar search by Co-I Nesvorný et al. (2003) yielded another
tight cluster around the outer‑belt asteroid 1086 Nata, within the
classical, unusually compact Veritas family (cut off from the rest
by a chaotic resonance). Because of the compactness (Fig. 2),
Milani & Farinella (1994) previously suggested that the Veritas
family is <50 My old. Nesvorný et al. (2003) analyzed the
evolution of nodal longitudes of relevant Veritas family members
(like the upper panel of Fig. 4) over 50 My, yielding (Fig. 5) a
prominent convergence of many orbits ~8.3 My ago. This is
surprisingly recent, given that disruptions of asteroids as large
as ~140 km diameter (the scale of the Veritas precursor body, Tanga
et al. 1999) occur rarely. Probably the Veritas family is really
older, but a smaller family member disrupted only ~8.3 My ago,
which produced Nata and those Veritas members that contribute to
the conjunction shown in Fig. 5. (The chance of this conjunction
occurring accidentally over the solar system's age is <10-5.)
Nesvorný et al. (2003) also describe why the small Iannini cluster
must be <5 My old, even though a specific date for disruption
cannot be calculated.
III. GOALS AND OBJECTIVES
Because we have determined the absolute ages of two very recent
asteroid collisions, we have the first and far‑reaching opportunity
to study time‑dependent phenomena that affect asteroids by
contrasting observations of these clustered asteroids with more
ancient asteroids. We have designed our three-year observing
program to test several predictions or expectations concerning very
young asteroids, in addition to looking for serendipitous
attributes of these bodies. Beyond our primary objectives
(described below), our data will also augment the general data sets
on asteroid physical properties.
Space weathering
Preliminary data, obtained by R. Binzel at our request, suggest
that Karin cluster members are S-like asteroids, like other Koronis
family members; Sloan Survey data of 3 others are also S-like.
Indeed one Koronis member, 243 Ida, has been a prime test case for
the existence of "space weathering" on S-type asteroids (Chapman
1996, Chapman 2004). Space weathering is the phenomenon, possibly
due to micrometeorite impact and solar wind impingement, that
modifies spectral reflectances from that of the inherent mineral
assemblage. Many S-types, for example, may be ordinary chondritic
(OC) in composition, but the diagnostic spectral shape and depth of
absorption bands are space weathered into a typical S-type
spectrum, characterized by a reddish continuum and shallower
absorption bands. Binzel et al. (1996) observed a full range of
spectra among small Near Earth Asteroids (NEAs), from OC to
traditional S-type, suggesting that there is a range of collisional
ages, with recently "freshened" surfaces looking like unmodified OC
meteorites (from lab spectra) while progressively older asteroids
are more maturely space weathered.
We would expect that Karin member surfaces are all the same age,
5.8 My (not to rule out some slight subsequent modifications). Our
low-res spectra will reveal the degree of space weathering (from
spectral slope and the 1 and 2 μm band depths). Since published
estimates of space-weathering timescales range widely from 50,000
years to 100 My (Hapke, 2001; Sasaki et al. 2001), it will be vital
to understanding space weathering processes to determine the degree
to which spectral evolution has matured on the 5.8 My-old Karin
family members. We can even test whether space weathering rates are
a function of body size, which might be expected if the processes
that comprise space weathering are mediated by regolith processes,
which in turn depend on a body's gravity. Thus the Karin cluster,
with its precisely known age within the range of space-weathering
timescales, presents a ready-made laboratory for testing space
weathering hypotheses. Such processes must affect C-type asteroids,
as well, although spectral effects may be smaller than for S-types
(cf. Sect. 7.2 of Rivkin et al. 2002); so we will make similar
observations of C-type Veritas family members. Indeed, this is a
perfect opportunity to understand how space-weathering differently
affects C- and S-types, calibrating the early changes before
maturity is reached. Space weathering processes are believed to be
material-dependent, so we are fortunate that our two young families
are so compositionally distinct (the taxonomy of the Iannini
cluster is not yet known, but we will study these exceptionally
young asteroids, as well, to determine their taxonomy). Our studies
will augment the partial understanding of space weathering already
achieved from spacecraft investigations of Ida and Eros (cf. Clark
et al. 2002).
Volatiles
Asteroids are generally thought of as rocky and comets as icy.
But water ice probably formed within the asteroid belt and could
have been stable for aeons within asteroid interiors, despite
readily subliming from asteroid surfaces. Indeed, there were
published 3 μm indications of water frost on Ceres, although that
is now largely discounted. The freshly created Karin and Veritas
asteroids provide our best chance to search for remnant water ice
(and other volatiles, like methane and CO2, all with characteristic
IR bands) on asteroid surfaces. For example, if the Veritas
precursor body had large chunks of ice within its deep interior 8.3
My ago, ice might have been at the surfaces of some fragments when
the family was created. Depending on ice thickness, it might still
be there to be detected, provided -- for example -- that it hasn't
been covered over by ejecta from a recent cratering event. One
might expect ice to be found in "dry" C-types (Rivkin 1997) in the
Veritas family rather than in either Karin cluster S-types, which
have been heated at least to metamorphic temperatures or in "wet"
C-types, which are inferred to have been thermally processed. Such
theoretical expectations deserve to be observationally tested, so
we will look at examples of each type. (Most, but not all, of
Veritas members are of the "wet" variety [Bus & Binzel 2002].)
Other ices and organic compounds might also last for millions of
years while generally vanishing on the longer time scales that
apply to typical asteroids. Since we can imagine that remnant ice
pockets might be much smaller in size than the family members
themselves, we propose to obtain spectra at higher S/N for these
compositional studies as well as at the somewhat higher spectral
resolutions that will reveal and distinguish volatile signatures --
accordingly, NIRSPEC on the Keck is our choice of instrument for
this purpose. The rather broad IR spectral bands of ices, hydrated
silicates, and organics can be intermingled (e.g. near 3 μm), but
much literature (e.g. as reviewed by Roush & Cruikshank 1994)
is devoted to resolving volatile compositions in the outer solar
system, and is applicable to interpreting our own data, which will
be obtained with similar observing techniques.
Satellite Formation and Evolution
Only a decade ago, asteroid satellites were a theoretical
curiosity. With the discovery of Dactyl during the Galileo flyby in
1993 (Chapman et al. 1995; Belton et al. 1995) and the first
verifiable detection from Earth of a satellite orbiting a main‑belt
asteroid (Merline et al. 1999), using adaptive optics (AO), we have
begun a revolution in asteroid science. Satellites of asteroids are
important (1) as natural laboratories in which to study the
cratering and catastrophic collisions that form and destroy them;
(2) because their presence permits determination of the primary
asteroid's bulk density, which is otherwise generally measurable
only by spacecraft missions; and (3) the evolution of satellite
systems (e.g. influenced by tidal forces) is related to spins,
configurations, and interior structures of the bodies involved.
Binaries have now been detected in various dynamical populations,
including Near‑Earth, main belt, outer main belt, Trojan, and
trans‑Neptunian objects (TNO). Detection of these new systems has
resulted from improved observational techniques, including AO on
large telescopes (applications to asteroids have been pioneered by
Co‑I Merline), radar, direct imaging, advanced lightcurve analysis
(mostly by Collaborator Pravec), and imaging by interplanetary
spacecraft (again led mainly by Co‑I Merline and PI Chapman).
Systematics and differences among the observed asteroid satellite
systems are revealing vital clues to the formation mechanisms.
A young family, like Karin or Veritas, presents an exceptional
opportunity to study the formation of asteroid satellites. Among
the three leading mechanisms for forming main‑belt binary
asteroids, one involves just the type of catastrophic disruption
that created the Karin and Veritas families (Merline et al. 2002b).
Early models of Durda (1996) and Doressoundiram et al. (1997), as
well as more sophisticated models being done by Durda et al. (see
Fig. 1) indicate that these systems (small primaries, with a
widely‑separated secondary) are commonly formed in catastrophic
collisions. Once formed, smaller satellites are subject to
collisional destruction on timescales of millions to tens of
millions of years. Therefore, members of recently formed families
would be especially likely, in this model, to retain observable
satellites; our understanding of asteroid collisional lifetimes
could be tested by searching for satellites among the members of
these young families, which have ages similar to the collision
lifetimes of satellites. Young asteroid satellite systems also have
had little time for significant tidal evolution of orbits or spins
‑‑ the system will be nearly "pristine", revealing the initial
spins and orbital configurations of first‑generation satellites
immediately following a catastrophic disruption. (Ida's Dactyl, in
contrast, is believed to be an nth generation satellite, having
been disrupted and reaccreted several times.) Timescales for tidal
evolution of the objects we consider here are quite long, some tens
to hundreds of millions of years (Weidenschilling et al. 1989).
Indeed, these are ideal systems to search for triple or multiple
systems! Expected characteristics of multiple systems are discussed
by Merline et al. (2002b). Current numerical models of satellite
formation by catastrophic disruption by Durda et al. (Icarus, in
press, 2004) indicate that soon after disruption many objects may
have multiple components. Our proposed observations could enable us
to study the lifetimes of such multiple systems, elucidating and
calibrating the dynamical stability of such systems and the
collisional mechanism that produces them.
In Feb. 2002, Merline et al. (2002a; 2002c) discovered what is
probably the first example of a binary system created by this
mechanism of disruptive capture (see Fig. 6). Among main‑belt
binaries, this system, 3749 Balam (a member of the Flora family),
at first stood out as an oddity: a very loosely‑bound system, even
more so than most TNO binaries. The secondary orbits at least 100
(primary) radii from the primary, which itself is just ~7 km
diameter. Because such systems are faint, only a few have been
searched for satellites before now. Because we expect the
separations to be large (binaries formed by the two other
mechanisms must have small separations), we can then make powerful
statements about the prevalence of satellites formed in
catastrophic collisions; in turn, this can guide the
now‑rapidly‑developing field of numerical simulations of satellite
and family formation. In Feb. 2003, Merline et al. (2003)
discovered another such widely separated system, 1509 Esclangona,
probably also the result of a disruptive capture.
We have been awarded a large HST program (Merline PI; Chapman,
Tamblyn, & Nesvorny Co‑Is) to search for satellites of small
Karin and Veritas members. We specifically chose limits that would
complement this proposed ground‑based search. The limits to
ground‑based AO are V=17.5, so our HST limits are V=17.5‑19.5. We
propose here to survey those objects brighter than V=17.5 so that
our study may span a larger size range (clearly, HST would not
support observations of brighter objects that could be made from
Earth). The faint limit (V=19.5) of our HST program was chosen to
provide satellite data on the fainter objects for which we will
obtain lightcurves, thermal, and spectral data in this proposed
groundbased program. We obtained the first positive results from
this HST program in the first download of data in July 2003, in
which we discovered a companion to asteroid 22899 (1999 TO14)
(Merline et al., 2003b). Although this object is not a Karin or
Veritas member, it is a Koronis family member that we are using as
a control. The primary is only 4.5 km diameter (making it the
smallest main‑belt binary known), and the companion is only 1.5 km
diameter (the size of Dactyl). Clearly, this wide binary is another
example of the systems we seek to observe here.
Calibrating the Yarkovsky Effect
The semimajor axis mobility caused by the Yarkovsky effect (Öpik
1951) has assumed major importance in understanding the long-term
dynamical evolution of asteroids, including delivery of meteorites
and NEAs to near-Earth space (e.g., Farinella & Vokrouhlický
1999, Bottke et al. 2002, Morbidelli & Gladman 1998, Morbidelli
& Vokrouhlicky 2003). Current models of the Yarkovsky effect,
however, rely on poorly known parameters that characterize the
composition and spin state of asteroids. Accordingly, Co-I Nesvorny
has developed a novel method that uses the Karin cluster to
precisely measure, for the first time, the semimajor axis mobility
that asteroids experience in the main belt (based on evolution to
current positions from a known time and location of formation).
To compare these drift rates with theoretical models of the
Yarkovsky effect, we wish to know as much as possible about (1)
size, (2) density, (3) albedo, (4) rotation rate, (5) obliquity,
and (6) surface conductivity of Karin cluster members. Here we
propose to determine attributes 1, 3, and 4 for representative
members; if satellites exist, we can determine density and our
lightcurve observations will start to constrain obliquity for some
objects. We may then calculate what values of surface conductivity
are compatible with the determined drift rates, thus constraining
the surface properties. In a broader sense, this work will allow us
to check, for the first time, theoretical models of the Yarkovsky
effect. Our work on this task will complement very recent radar
efforts that successfully detected the Yarkovsky effect on a
natural body, 6489 (Chesley et al. 2000, 2003). Rather than NEAs,
our studies concern a large sample of multi‑km asteroids, with
various sizes, obliquities, and spins in their main-belt
environment.
Checking Hydrocode Simulations of Asteroid Disruption
We and our colleagues are undertaking SPH simulations of the
catastrophic break-up of asteroids, including the Karin cluster
parent body (see Fig. 1). Obtaining good data on the physical
attributes of the immediately post-break-up Karin cluster (and
other young clusters) will help us better understand the physics of
large‑scale collisions, the mechanism that helped shape the planets
at early epochs (Chambers & Wetherill 1998, Canup & Asphaug
2001). To correctly set up numerical experiments and check results
against ground truth, we need to observe and determine the sizes,
densities, and spin properties of Karin cluster members.
Broader Social Context and Public Outreach
Our research objectives concern the processes that created
asteroids and cause their continuing evolution, including delivery
of some of them (and their fragments) from the asteroid belt to
Earth. Asteroids, as well as the Sun, are the two parts of the
extraterrestrial universe that have direct manifestations on Earth.
In the case of asteroids, the direct relevance is the continual
rain of bolides and meteorites onto our planet, as well as the
(very low-probability) threat of devastating impacts by 100-m to km
scale asteroids, like those that have helped shape the biological
evolution of our planet. Thus it is not surprising, for instance,
that past NASA Administrator Goldin reportedly said that
"asteroids" ranked second in the number of letters he received from
the public. Thus we asteroid researchers have fortunately been on
the frontlines of interfacing with children and adults alike, whose
curiosity about asteroids and the potential hazards they present
are often their first introduction to astronomy or even
science.
The P.I., Dr. Chapman, has had a lifelong commitment to
education and public outreach, which was recognized by his being
awarded (1999) the AAS DPS Carl Sagan Medal for "Excellence in
Public Communication in Planetary Sciences." His activities, almost
wholly unfunded, have included writing popular books and articles,
appearing in TV documentaries (like Nova), curating a museum
science exhibit, giving classroom and public lectures,
participating in moderated web-chats (e.g. concerning
Astrobiology), responding to journalist inquiries, and so on. He
currently serves as Liaison between the Science Team and the EPO
effort of NASA's MESSENGER mission to Mercury. Dr. Chapman's EPO
activities within several weeks of the submission of this proposal
(mid-Nov. 2003) are representative: (a) answering dozens of
inquiries from the public concerning a feature article in the Nov.
Scientific American co-authored by Chapman; (b) publication of an
essay co-authored by Chapman (selected by Richard Dawkins) in
Houghton Mifflin's "The Best American Science and Nature
Writing--2003"; (c) co-author of a MESSENGER EPO talk at Fall AGU
and invited author of an interdisciplinary plenary Union talk at
AGU; (d) public evening talk about asteroids at Little Thompson
Observatory in Berthoud, Colorado; (e) invited submission of
Letter-to-Editor of New York Times concerning science journalism;
(f) appearance on 2-hr CBC/BBC-TV documentary on asteroids Nov.
24th; (g) participation (with astronauts Rusty Schweickart and Ed
Lu) in activities concerning a possible asteroid mission through
the public B612 Foundation; and (h) coordination of EPO activities
in the Boulder Office of SwRI. Several other Co-Is of this proposal
often engage in similar activities.
We are thus pleased with NSF's encouragement of such activities
and have a specific goal of emphasizing the public dissemination of
our research activities in numerous different ways as our research
progresses. Some of these EPO activities will be proactively
arranged by us, while others will arise serendipitously, since Dr.
Chapman and other Co-Is are frequently solicited by teachers,
museum staff, etc. to participate in EPO projects. We will
specifically try to explain in ways accessible to the lay public
the rather technical project that we propose herein, but we expect
that most of our EPO efforts will relate to asteroids more
generally, in ways immediately relevant to public curiosity. There
is, after all, a connection between our trying to learn about
asteroid collisional processes by studying the youngest break-ups
(before the family members have dispersed or been modified by
subsequent collisions or space weathering) and the public
fascination with rocks -- and potentially bigger objects -- falling
from the skies: the collisions and subsequent evolution of
fragments that we are investigating are the very processes that
bring asteroid fragments from their distant, harmless orbits beyond
Mars to make their fiery impacts onto our planet.
IV. TECHNICAL APPROACH
Introduction and Scope of Observations
We have compiled lists of known members of the Karin cluster
(a=2.87 AU, e=0.044, i=2.1º), the Veritas family (a=3.17 AU,
e=0.065, i=9.3º), and the Iannini cluster (a=2.64 AU, e=0.267,
i=12.2º), giving the brightest V magnitudes attained by each object
during the 3½ years after our nominal 1 July 2004 start date (space
limitations preclude presenting these lists in this proposal).
Roughly 74 Karin family members, 207 Veritas members, and 25
Iannini cluster members are at least briefly brighter than V=19.5.
(Based on the current rate of continuing discoveries of main-belt
asteroids and calculations of family assignments, we expect these
numbers to escalate to roughly 115, 395, and 48, respectively, by
2006.) Therefore, we expect that on a typical night (Mauna Kea,
zenith dist. <65º) there will be about 15, 130, and 9 known
members visible brighter than V=19.5, respectively; hence
scheduling observations to achieve our statistical samples of Karin
and Veritas members is not a problem. Fewer objects will be
available at Mauna Kea during the first year-or-so of our program
until a planned new guider is installed that will work fainter than
V=18; also, for some of our other proposed studies, magnitude
limits are brighter than 19.5, so we will concentrate on brighter
objects that are available. Fig. 7 shows V magnitudes for those
Karin and Iannini family members that are currently known (i.e. not
escalated to 2006), during the 3½-year period beginning July 2004
during which this program will be conducted, showing the number
that rise brighter than various magnitude limits for the types of
observations discussed in this proposal.
Our program uses several different observational facilities and
instruments, each carefully chosen and suited to a specific task.
We have previous experience proposing for and using these
facilities. Our track record shows that we can successfully compete
for time at large telescope facilities. Due to the usual vagaries
of telescope time assignment, weather, etc., we cannot specify
which particular asteroids we will succeed in observing with which
combination of observing modes, nor to exactly what level of S/N.
Our approach is not to observe every member (after all, many
members remain to be discovered!), but rather to observe (a) many
of the known Karin cluster members, (b) a large, representative
sample of Veritas family members, and (c) many of the Iannini
objects (a small cluster that nevertheless has some moderately
bright members). We will try to cover as wide a range of sizes for
each group as possible with each technique, emphasizing brighter
objects but giving some priority to the longer integrations needed
to obtain a few fainter objects.
Our approach will generally be to obtain data similar to data
that have already been obtained -- often with the same telescopes
and instruments -- for other main-belt asteroids by other
observers. By using similar observing modes and data reduction
procedures, our data can readily be compared with other archived
data, in order to clearly detect differences among young family
members and other categories of asteroids. Our observations will be
made with spectral resolution and S/N, using facilities specified
in Table 1 (keyed to goals by abbreviations), so as to address
several key determinable properties of the individual members of
these dynamical families:
* SW: slope of the near‑IR spectrum and absorption band
parameters, which define the extent of space weathering on these
bodies, obtained at low spectral resolution.
* TAX: taxonomic type of the objects, which will help relate
these bodies compositionally to those in other families (e.g. as
observed elsewhere in the main belt by Bus, 1999). (Note: although
taxonomy was traditionally defined in the visible and near-IR,
later studies demonstrate the correspondence of types as measured
in the 0.8‑2.5 μm range.)
* SPIN,SHAPE: object spin periods and lightcurve amplitudes,
which can be analyzed in the context of similar data for other
asteroids, relevant to body shapes and dynamical evolution. In some
cases, we can obtain lightcurves from several geometries,
permitting us to determine or constrain obliquities (P.I. Chapman
is familiar with this approach as a participant in the PSI
Photometric Geodesy program, cf. Weidenschilling et al. 1987).
* SIZE,ALB: thermal flux measurements, which, together with the
visible lightcurves (taken simultaneously, or nearby in time, such
that we know the lightcurve phase during the radiometric
observations), will yield albedos and sizes of the objects, using
the Standard Thermal Model and more sophisticated techniques (cf.
Lebofsky & Spencer 1989).
* SAT: existence of (or limits on sizes of) satellites of the
objects.
* VOL: medium resolution spectra of a selection of the objects
to search for (or set limits on) the presence of ices or other
volatiles, which may have survived since break-up on or near the
surfaces of some young objects.
Our baseline schedule of observing runs is outlined in Table
I.
Table I. Summary of Planned Observing Runs
Year Run# Where # # Instrument Measurement Science
Nights Persons Goals
1 1 Keck 2 2 NIRSPEC MRES VOL
1 2 VLT 2 2 NACO AO SAT
1 3 IRTF 5 2 SpeX/MIRSI LR;TH SW,TAX;SIZE,ALB
1 4 Arizona 7 2 CCD photom LC SPIN,SHAPE
2 5 IRTF 5 1 SpeX/MIRSI LR;TH SW,TAX;SIZE,ALB
2 6 Keck 2 2 NIRSPEC MRES VOL
2 7 VLT 2 1 NACO AO SAT
2 8 IRTF 5 1 SpeX/MIRSI LR;TH SW,TAX;SIZE,ALB
2 9 Arizona 7 1 CCD photom LC SPIN,SHAPE
3 10 Gemini 2 1 Altair/LGS AO SAT
3 11 Arizona 7 1 CCD photom LC SPIN,SHAPE
3 12 IRTF 5 1 SpeX/MIRSI LR;TH SW,TAX;SIZE,ALB
3 13 IRTF 5 1 SpeX/MIRSI LR;TH SW,TAX;SIZE,ALB
In addition to the specific runs tabulated here, there will be
numerous opportunities to acquire lightcurve data through the local
Univ. of Colorado facility and via our Czech Collaborator P.
Pravec, during some of his regularly‑scheduled observing nights.
Efforts will be made to coordinate observations of this program
with other runs we may fortuitously have on any of these same
telescopes.
Key:
LR = low‑resolution spectra 0.8‑2.5 μm; R~25
TH = thermal IR radiometry, N band (10.6 μm); 20 μm, weather
permitting
AO = high-spatial-resolution near-IR imaging by adaptive optics
(resolution ~0.05 arcsec,
or ~70 km at the range of the Veritas family)
LC = time‑resolved visible photometry to determine the
lightcurve
MRES = medium‑resolution spectroscopy (R~100) over the range
2.2‑4.2 μm
"VLT" is the ESO Very Large Telescope Facility, located on Cerro
Paranal, in Chile. It is a complex of four 8.2‑m telescopes; one
telescope is dedicated full time to the NACO AO facility. NACO
combines their new Shack‑Hartmann AO system, with CONICA as the
science imaging detector (InSb detector, 1024x1024, 1‑2.5 μm). We
already have European collaborators for the VLT AO program of
Merline et al. (and demonstrated performance down to V = 17.4). But
Co‑I Nesvorný and Collaborator Pravec, both Europeans, will qualify
our proposals as "European", and thus they cannot be downrated
because of lack of European participation.
"Arizona" represents an as‑yet unspecified site within Arizona:
KPNO (NOAO), Lowell Observatory, Vatican (with whom we've already
had informal discussions), Univ. of Arizona Observatories (UAO),
Planetary Science Institute (PSI). For our lightcurve work on
objects fainter than V=17.5, we require a ~2-m class telescope, of
which there are many. We expect access via our numerous
collaborations and/or through normal TAC process (such as to NOAO).
Examples include Lowell 72", Kitt Peak 84", PSI‑operated Kitt Peak
50", UAO 61" & 90", and Vatican VATT 1.8‑m (among us, we have
used all of these example telescopes in the past). CCDs for
photometry are common astronomical instruments and we anticipate
access to a CCD at any of the above sites (we, at SwRI, also have
our own CCD camera that would be suitable).
"Altair/LGS" is a planned upgrade to Altair, expected to be
ready for operation in 1-2 years. Altair is just now being brought
on‑line using natural guide star (NGS), i.e. guide‑on‑target.
Altair in NGS mode will be able to achieve good AO‑correction on
objects only down to ~15.5 Vmag. Therefore, laser‑guide‑system
(LGS) will be required to observe many of our targets. Once LGS is
available, we should be able to achieve AO‑imaging of V=17.5
targets.
We now provide more details on how each suite of observations is
designed to address a particular goal with an efficient set of
measurements.
Spectrophotometry, Spectroscopy, and Radiometry
We will obtain low resolution spectra (R=~25) to address space
weathering phenomena on the very young surfaces of cluster members
and to confirm or derive taxonomic type. We will use the IRTF SpeX
in its lowest resolution (but most sensitive) 0.8-2.5 μm "prism"
mode. The SpeX online documentation (http://irtfweb.ifa.hawaii.edu/
Facility/spex/sensitivity.html) recommends 120‑sec A‑B beam switch
pairs, since longer exposures would potentially fail to remove
variable OH sky emission lines; with the object in an 0.8" slit in
both the A and B positions, S/N ~10 is expected for an hour
integration (15 A‑B pairs) for J‑mag. 18.9, H‑mag. 18.4, or K‑mag
17.9 (equivalent to V~20 for a typical asteroid). The 0.8" slit
produces resolutions R=60 in J, R=100 in H, and R=140 in K, but we
plan to bin in wavelength to R=25, which will yield spectral
resolutions about half that of the 52‑color data set of Bell et al.
(1988), sufficient to study space weathering and classify taxonomy.
Such binning improves the S/N by factors of 1.6, 2.0, and 2.4 in J,
H, and K filters, respectively. The S/N for a 19.5 mag. object
(observable when the planned upgrade to the tracking system is
finished) is ~12 in all three filter regimes (for 1 hour, binning
R=25).
There are 74 Karin cluster objects and 207 Veritas objects that
achieve brightness greater than 19.5, rising to 115 and 395 by
2006. An average of 154 Karin, Iannini, and Veritas objects
brighter than 19.5 magnitude will be available at each run by 2006.
(The current TCS [telescope control system] can track objects only
brighter than V=18; it is expected to be upgraded within 18 months,
but even if it isn't, we still would have ~30 objects available per
run, more than we can observe.) We expect to observe 10 objects per
night (at 1 hour per object, and allowing time for focus,
calibration, and standard stars), achieving S/N of 12 for the
faintest objects (mag 19.5), sufficient to specify spectral slope
and assign taxonomic class, and rising up to about S/N~50 for the
brighter ones. We have planned 5 observing runs of ~4 nights each.
If we conservatively estimate an overall time loss of 50% for
weather and equipment problems, we will conservatively obtain
spectra of 20 objects in a 4‑day run with S/N of 12. The expected
total will be >100 objects over the duration of the entire
project. Our reduction of SpeX data will use the IRTF's SPEXTOOL
package. Its current version (3.1) fully supports low-res prism
spectra. It does a nice job of dark and bias subtraction, flat
field normalization, arc lamp and sky line identification, and
wavelength calibration. It also evaluates noise on a per‑pixel
basis and propagates errors through the spectral extraction
process. (There are some who are skeptical about our proposed use
of standard SpeX reduction techniques. But Co-I Young is thoroughly
practiced in obtaining excellent data with SpeX; he was awarded 5
nights on SpeX this past semester [2003 A], 3 as PI, 2 as Co‑I. In
separate research, Co‑I Young is funded to develop a pipeline for
reducing data from IRTF instruments.)
From IRTF/SpeX low- res (R~25) spectrophotometry of cluster
members having a range of brightnesses, we can address how space
weathering of equal-aged bodies varies with size. However, even the
brightest few Karin cluster members are difficult targets from SpeX
in higher resolution modes; accordingly we will request
Keck/NIRSPEC time to observe a few Karin, Veritas, and Iannini
cluster targets with higher spectral resolutions and better S/N to
search for volatiles. Spectral resolutions of R=100 or higher are
preferred for this search (translating to binning factors of 22x
for NIRSPEC spectra). Even if we find no volatiles, the negative
result will establish an interesting upper limit. To make the
search more sensitive, we plan to obtain a S/N of 30 (or better)
per binned wavelength sample. Based on Co-I Young's experience
observing the Centaur Chariklo (V‑mag = 17.79) with NIRSPEC at
R=2,200 (see Fig. 8), the brighter Karin and Veritas members should
be straightforward spectral targets, even with our nominal S/N
requirements. We plan two Keck observing runs over the 3‑year span
of our project. The result will be medium-res spectra generally
over 2.2-4.2 μm of ~1 dozen objects, giving us an adequate sample
to examine for presence of volatiles. We will use the KL
order-sorting filter with NIRSPEC "LoRes" mode (R=2200 binned to
R=100), with total on-target integration times ~90 min. We will
restrict our observations to objects brighter than V~18. Again,
there will be plenty of targets for any run, but we will optimize
our observing time requests to study the most objects.
Thermal flux measurements will be made at IRTF using the MIRSI
mid‑IR camera; we will make appropriate arrangements with the P.I.
of this new instrument. Radiometry at 10.8 μm (N‑band) will be used
to determine the albedos of a select number of brighter family
members. When conditions warrant, we will also attempt observations
at 20 μm, which permits a better handle for modelling the
asteroidal emissions. Observations in these two bands have been
classically used in asteroid radiometry. We expect observational
limits of V~16-17 for MIRSI; we will schedule observing requests to
optimize the number of targets. We plan to use both SpeX and MIRSI
during the same observing runs; we therefore budget one additional
night per run for MIRSI. As with MIRSI's predecessor MIRLIN, we
expect that MIRSI and SpeX can be routinely swapped within an
observing run (indeed within a single night); thus we can make best
use of atmospheric conditions (determined by 225 GHz opacity) to
select the best times to use MIRSI within a 5‑night run. We would
expect to have about 6 objects observable (including Veritas
members, not shown in Fig. 7) during a well-chosen run.
Adaptive Optics Observations
We will also perform adaptive optics (AO) observations of some
family members to search for companions. Because these objects are
faint, the only currently capable system (down to V=17.5) is the
NACO system on the ESO Very‑Large‑Telescope (VLT) in Chile. Merline
et al. have completed two VLT observing runs, discovering yet
another binary of the type we propose to study, around (1509)
Eslangona (Merline et al. 2003a). That program targets certain
main‑belt and Trojan asteroids, but not Karin, Veritas, or Iannini
members. We expect success in acquiring time (one run per year)
during the first two years of this project. In the final year we
will use the Gemini telescope (Altair); Merline et al. have used
Gemini to great effect to search for satellites of faint asteroids,
but the Altair/LGS will not be available until 2004-2005, at which
time Gemini is preferred because we expect shorter exposures due to
the brighter laser guide source with the new LGS system, and thus
sharper target images.
Using either NACO or Altair/LGS, we will be able to search for
satellites around the brightest Karin family members; several
Iannini and many Veritas members will also be accessible. The
limiting magnitude at VLT is ~17.5 Vmag, but we expect Altair/LGS
to allow us to work fainter, maybe even to V ~19.5. Based on our
previous experience, we expect to observe 20 objects per good night
at VLT and 40 per night at Gemini. We have thus budgeted 3 total AO
runs. At 2 AU from Earth, we will resolve objects separated by
~70km at brightness ratio ~3 mag. Thus, for a 10 km primary, we
could detect a 2.5 km sized satellite at separation 70 km (~5
primary radii). The targets of our search in the proposal will be
systems formed by family formation, probably co‑orbiting pairs
(unlike most known main‑belt binaries, which formed by large
cratering events), so we expect large separations for these
binaries (see Weidenschilling et al. 1989; Merline et al. 2002b);
thus, our secondary size limits will be even better. Under
Merline's AO program, we have developed tools to predict appulses
of faint asteroids with bright stars. For our three clusters, we
expect to have a few dozen events per run. By guiding on the bright
star near the asteroid we can temporarily achieve good AO
correction on the asteroid (provided it is within the isoplanatic
patch of the star, which is ~20 arcsec in the near‑IR).
Lightcurve Photometry
Lightcurves of the cluster members will be acquired by 3
strategies:
* For objects brighter than about V=17.5, we will employ
existing facilities at the Univ. of Colorado campus, which will
allow ~3% photometry using the 24" telescope and new SiTe CCD. SwRI
scientists (some of us are Adjunct Faculty at CU) routinely use
this telescope for photometry. By observing locally, we avoid
travel costs.
* Our collaborator Pravec will also acquire lightcurve data, at
the same precision, on his 0.65m system in Europe. An advantage is
that we can obtain better phase coverage and quicker solutions for
spin periods. Furthermore, multiple observations help us resolve
ambiguities, and in particular give good lightcurve coverage in the
case of an eclipsing binary. Pravec has regular and routine access
to this telescope.
* For objects fainter than V=17.5, we will obtain lightcurves
with one of several Arizona telescopes. We have budgeted one trip
per year to Arizona for a week each. We expect to obtain
lightcurves on as many as a dozen objects during a good night,
using standard photometric procedures and the protocol of the PSI
Photometric Geodesy (in which P.I. Chapman participated; cf.
Weidenschilling et al. 1987). Allowing for 50% loss to weather we
would get lightcurves on ~125 fainter asteroids over 3 years,
enough to characterize the spin‑distribution and shape
characteristics of these compact, recently formed clusters.
TABLE II. Summary of Expected Observations
Obs S/N Resol. # Nights # Objects # Objects # of Total
Objects
Type per run per night per run (*) Runs (3 years) (*)
LR ~20 25 4 10 20 5 100
TH ~30 ‑ 1 6 3 5 15
MRES ~30 100 2 6 6 2 12
AO/VLT ‑ 70km 2 20 20 2 40
AO/Gem ‑ 70km 2 40 40 1 40
LC 30 ‑ 7 12 40 3 ~125
* = assumes 50% loss due to weather, equipment, etc.
Analysis and Interpretation
Our data will be reduced using standard (but enlightened)
procedures, for each of the different techniques employed, with
which we are already intimately familiar. The assembled data (Table
II) will be intercompared among family members and with more
typical asteroids. We will analyze and synthesize the data in order
to obtain first-order answers to the questions posed in our
Objectives; we must frankly state, however, that the majority of
time budgeted in this proposal is for data acquisition and
reduction, and we must seek additional funding elsewhere for
thorough analysis of the data. Of course, these asteroid clusters
are so exceptionally young that we expect some rather obvious
results will become immediately apparent as the program proceeds.
Should unexpected phenomena be revealed, our ongoing analyses may
suggest changes in our observing priorities. We will give more
priority to presenting, publishing, and archiving our data and
first-order results in our second and third years, and have
budgeted an additional science conference for the final year.
Public Outreach
We outlined in Sect. III our deep commitment to, and experience
in, Education and Public Outreach (EPO) activities. Because of the
intense public fascination with asteroids and their (literal)
impacts on Earth and in the news, as well as the prominent public
roles the P.I. and some Co-Is continue to play in this topic, we
expect to continue to receive solicitations for future public
outreach opportunities related directly, and more commonly
indirectly, to our proposed asteroid research (note: in our
non-academic, non-profit research institute, public outreach
efforts are normally a better fit for us than formal education
activities). We will continue to respond positively to such
invitations, which normally involve hundreds of unfunded hours
(mainly evenings and weekends) per year. In addition, to
demonstrate our commitment to these endeavors, the P.I. has
budgeted 20% of his participation in this proposed research to lead
and conduct public outreach activities, related to asteroids,
during this three-year program. These will include writing at least
one article per year (for public print- or web-magazines) and
arranging to give at least one public presentation per year (e.g.
to schools, museums, planetariums, service organizations) on
asteroidal topics at least indirectly related to our research.
Many EPO activities emphasize two factors: (a) effective
leveraging of the scarce, valuable time of often busy and
inarticulate scientists, usually accomplished through
intermediaries such as professional educators, and (b) formal
evaluation of effectiveness in meeting, for example, goals of
national science education standards. In our case, Drs. Chapman,
Merline, Young, and Nesvorny are all articulate, experienced
speakers and writers for the lay public, and we are sought after by
entities that can bring our direct message to dozens or up to
millions (in the case of TV and radio) of children and adults; for
that reason, we believe our limited time is most effectively used
in being directly engaged in public outreach activities rather than
in attempting to coordinate with EPO professionals. It will be less
easy for us, in these often informal settings and involving media
(like TV) beyond our control, to formally assess the effectiveness
of our public outreach activities. But we will be diligent and
cognizant of the need to be effective in our communication; we will
engage in activities that reach many people and have good chances
of continuing to spread beyond our immediate readers and listeners
to others of diverse ages, ethnicities, and interests. In
conclusion, we emphasize our past record (highlighted in Sect. III)
of nationally-recognized EPO activities as the best guage of our
promise to share effectively the larger insights and relevance of
our research with the public.
V. WORK PLAN, PERSONNEL, PUBLICATIONS, DATA PRODUCTS, EQUIPMENT,
AND BUDGET NOTES
Dr. Clark Chapman, as P.I., will oversee the entire research
project. He will co-lead the low-res spectrophotometric and
lightcurve photometry portions of the project and will play a major
role in the analysis, interpretation, and synthesis of the data; he
will commit 20% of his time to leading public outreach efforts. Dr.
William Merline will lead the adaptive optics observations, co-lead
the lightcurve photometry, and contribute to reduction of all of
the observational data. Dr. David Nesvorny, who led the theoretical
analysis that discovered exceptionally young families and clusters,
will participate in some observations and will lead the first-order
interpretation of the data for the relevant physical processes that
we are exploring. Dr. Eliot Young will lead our moderate-resolution
spectral studies using NIRSPEC and co-lead the IRTF
spectrophotometric observations; Dr. Young leads a NASA‑funded
project for IRTF data reduction. Dr. Peter Tamblyn will lead the
planning and coordination of our observing runs and will contribute
to data reduction. Our overseas Collaborator, Dr. Petr Pravec, is
one of the world's most productive lightcurve observers (cf. Pravec
et al. 2002) and will obtain many of the proposed lightcurves. Drs.
Merline, Nesvorny, and Young will also contribute to the public
outreach efforts led by Dr. Chapman.
We expect to work more-or-less continuously on all observational
tasks throughout the three years, emphasizing analysis, synthesis,
and publication in the third year. As is true of most observing
projects, we cannot be assured in advance that we will get
telescope time (or be rewarded with working equipment and clear
skies), but we have an excellent record of obtaining time (and
making good use of it!) on the most competitive telescopes in the
world. For example, Dr. Merline (generally with co-I Chapman) has
been awarded time (often multiple observing runs) during the last
several years on HST, Keck, Gemini, CFHT, Mt. Wilson, and Palomar.
Dr. Young has been a frequent observer on the IRTF; he has also had
several Keck/NIRSPEC runs. Drs. Chapman and Merline have frequently
used numerous facilities in Arizona (e.g. the Vatican Observatory
and KPNO telescopes), and will arrange to use nearby telescopes in
Arizona, Colorado, and/or New Mexico for purposes of our lightcurve
observations. (Since telescope allocations are made in TAC
processes wholly divorced from this proposal, we cannot know now
when we will get time, so we obviously cannot detail our observing
or work schedule more precisely.)
Our travel budget supports 13 formal observing runs. The
facilities are carefully chosen to yield maximum scientific return
at lowest cost. We budget 5 trips to IRTF, and within each run we
combine our SpeX and MIRSI goals so as to avoid additional travel.
For each facility we budget travel for 2 observers for only the
first trip to that facility for this program. We firmly believe
that this is required for efficiency, to prevent overloading one
observer in starting this new program, and to refine observing and
reduction techniques. Subsequent runs will be made by just one
observer, which should be adequate once we know our routine.
Indeed, we hope to take advantage of remote-observing opportunities
(e.g. at IRTF), but we cannot judge whether they will suffice for
our challenging program; thus we conservatively budget for these
trips, while hoping that we can eliminate the costs for some trips
in this way (our budget does take account of the fact that some
observatories pay for some or all travel expenses; e.g. NASA/Keck
time now comes with nearly full travel funds). In any case, we will
have additional observers on‑line, in real‑time, from the home
institution during most runs, to assist decision‑making and data
reduction. Our remaining travel is very modest: 3 scientific
meetings; actual travel costs will be determined by the market, but
we are obliged to budget them under current prices and guidelines.
In addition to these trips, we will perform, with no travel costs,
multiple "runs" using the Univ. of Colorado facility (<2 miles
from the SwRI office) to acquire lightcurve data on brighter
targets; such observations are not technically demanding. We will
also be assisted by Collaborator Pravec, who will acquire
lightcurve data at no specific cost to this project.
We seek support for a total of 3 meeting trips for one person to
present our results. We budget these as one DPS meeting in the
second year (it is in the U.K.); in the 3rd year we budget one DPS
meeting and one AGU meeting. The required labor is calculated to
allow coverage of planning (1 day per run), travel (1‑2 days per
run depending on location), making the observations, and data
reduction (time equivalent to the sum of planning, observing, and
travel for that run; e.g. a 7‑day run requires ~7 days of data
reduction). Thus planning, observing, and data reduction consumes
about half of our labor allocation. The remaining 50% is allocated
to local lightcurve observations, first-order data analysis and
interpretation, presentation of the results at meetings, archiving
our data (perhaps in the PDS Small Bodies Node, but certainly on a
publicly-available website), and publications in peer-reviewed
journals; note that SwRI will pay any page charges for these
publications. We will regularly report progress at professional
meetings and colloquia and will promptly publish our data and,
eventually, our interpretations in the peer-reviewed literature,
once we have reduced sufficient subsets of data or reached
important insights.
We require no funds for observational instrumentation or
equipment and have no archived data requirements. SwRI provides all
computer hardware, software, routine computer support, and data
storage capabilities. We call attention to the "Science Proposal
Budget Notes and Institutional Contributions at Southwest Research"
in the budget section, which explains in part how -- in spite of
the appearances of the unusual accounting procedures that we are
mandated by government auditors to use -- our budgeted work is
actually very cost-effective.
VI. RESULTS FROM PRIOR NSF SUPPORT
The P.I. has received no NSF support during the past 5 years.
Results from NSF awards for two Co-Is (Drs. Nesvorny and Merline)
are reported below.
Dr. David Nesvorný. NSF Award #0307926. Formation of Kuiper Belt
Binaries and Planetary Satellites. $60,572 per year from 07/01/03
to 06/30/06 (continuation of NSF award #0074163, Dynamical Studies
of Planetary Satellites).
This award resulted in 6 publications in refereed journals,
several conference talks, press communications and public lectures.
Our results include: (i) Present systems of satellites at Uranus
and Neptune are only compatible with much less planetary migration
than suggested by previous studies. (ii) A study that revealed the
importance of collisions between irregular satellites of the Jovian
planets with implications for imaging of Phoebe's surface during
Cassini's close flyby in June 2004. (iii) Year 2002 prediction that
Trojans of Neptune exist; the first Trojan of Neptune, 2001 QR322,
was discovered in early 2003 by the Deep Ecliptic Survey ‑‑ a
survey that uses the National Science Foundation's telescopes at
Kitt Peak National Observatory in Arizona and Cerro Tololo
Inter‑American Observatory in Chile. (iv) Identification of dozens
of asteroid fragments from the most recent catastrophic collisions
that occurred in our solar system. The 6 publications are: Beauge
et al. (2002) and Nesvorný et al. (2002a, 2002c, 2003a, 2003b,
2003c).
Dr. William J. Merline. NSF Award AST9802030. A Ground‑based
Search for Asteroidal Satellites using Adaptive Optics. PI: William
J. Merline, Co‑Is: Clark R. Chapman, David Slater.
10/1/1998‑9/30/2001, total funding: $99,961. And NSF Award
AST98726. Search for Asteroidal Satellites Using Adaptive Optics.
PI: William J. Merline, Co‑Is: Clark R. Chapman, David C. Slater;
Other Professionals: Laird Close, Christophe Dumas, Chris Shelton,
Francois Menard. 10/1/2001‑9/30/2004, total funding $136,292.
These two projects embarked on the first dedicated survey of a
large number of asteroids (hundreds) for the presence of
satellites. They resulted in the detection of the first known
asteroid satellite from Earth (HST or ground‑based) when 45 Eugenia
was found to be binary in 1998. It was only the second known
binary, after 243 Ida. This team has now discovered 11 of the 16
known binaries among the main‑belt and Trojan asteroids. Among the
"firsts" are the detection of the first (and only) true double
asteroid (components of the same size) (90 Antiope), the first and
only Trojan binary (617 Patroclus), and the first binary thought to
be formed by a catastrophic collision of the type sought in this
proposal (3749 Balam). We now see that at least 3 mechanisms must
be responsible for formation of the main‑belt binaries, and the
observed systems appear to be falling into well‑defined clusters of
parameter‑space characteristic of these formation mechanisms. We
also see differences in characteristics and frequency between
C‑type and S‑type systems. Our survey has studied >600
asteroids; the binary frequency among main‑belt asteroids is low,
~2%. Our work has permitted determination of the densities of some
primary asteroids (in binaries); we find that all C‑types have
densities 1.0‑1.5 g/cc. Major publications resulting from our work
include Merline et al. (1999c) and Merline et al. (2002b), along
with many IAU Circulars (e.g. Merline et al. 2002a, 2003a).
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Figures and captions to be moved up into text:
Fig. 1 New test‑of‑concept simulations of catastrophic
disruption, at scale of Karin cluster creation. Shows the system 35
min. after a 3‑km impactor collides with a 25‑km target, at 5 km/s,
with impact parameter 0.26 target radii (impact angle 15º). A
collaborative Artificial Intelligence computational effort of SwRI
and JPL (involving Co‑Is Merline and Nesvorny, P.I. Chapman, among
others at SwRI, using modeling codes of E. Asphaug and D.
Richardson).
Fig 2. Major asteroid families in the main belt. All currently
known members for each family are plotted in aP,eP projection.
Symbol size reflects asteroid size. Some families are more tightly
clustered, perhaps reflecting recent breakups. The Veritas family
at 3.17 AU has an especially small spread in aP, which contrasts
with much larger spread of the Koronis family at 2.9 AU. These two
families correspond to breakups of two similarly‑sized parent
bodies (Marzari et al. 1995, Tanga et al. 1999). The Koronis family
has been dispersed by the Yarkovsky effect over ~2‑3 Gy (Bottke et
al. 2001). We also show several mean motion resonances (dashed
lines), and a well-known "secular resonance" (Williams 1969)
involving Saturn.
Fig. 3. The Karin cluster's orbital structure implies a recent
asteroid break-up: (a) aP,eP and (b) aP,iP. The size of each solid
symbol reflects the diameter of a cluster member. Small x’s are
background Koronis family bodies. The ellipses show the orbital
elements of test bodies launched at 15 m/s. The good match between
ellipses and the observed cluster indicates that it must be <10
My old ‑‑ otherwise the dynamical dispersion that modified other
known families would prevent a good match (Nesvorný et al.
2002).
.
Fig. 4. The convergence of angles at 5.8 My ago means that the
Karin cluster was created by a parent asteroid breakup at that
time. The plot shows past orbital histories of Karin members: (a)
nodal longitudes and (b) perihelion arguments. Values relative to
832 Karin are shown. At 5.8 My ago (broken vertical line), the
nodal longitudes and perihelion arguments converge.
Fig. 5 from NASA PAST proposal
Fig. 5. The convergence of nodal longitudes at 8.3 My ago
suggests that the Veritas family was formed by a catastrophic
collision at that time. The bottom plot shows past orbital
histories of nodal longitudes relative to 1086 Nata. The average
nodal longitude (top plot) of 40º at t=‑8.3 My, is much smaller
than at other times.
Fig 6 from NASA PAST proposal
Fig. 6. Discovery image of S/2002 (3749) 1, a satellite of
asteroid 3749 Balam, acquired by Merline et al. (2002a,c) on Feb.
8, 2002, using the Gemini Hokupa'a AO system. This
asteroid/satellite system is similar to those we propose to
discover. The primary is ~7 km diameter, the secondary 1.5 km (the
size of Dactyl). If observed at 2 AU, this system would be about
V=17, with separation 0.25 arcsec, well within the capabilities of
the AO systems we propose to use. This system is the most
loosely‑bound system known, even more so than the Kuiper Belt
binaries, well beyond the Hill sphere. This is likely the first
example of a binary asteroid created during a catastrophic
disruption; most other main-belt asteroid satellites orbit ~10
orbit radii and probably formed by other processes.
Fig. 7. Visibility of Karin (dotted) and Iannini (dashed) family
members from a representative observing site (Mauna Kea), 1 July
2004 to 31 December 2007. Here, the large, bright asteroid 1379
Nele is included within the Iannini family, although that
assignment is uncertain; our observations may resolve whether or
not it is an interloper. The horizontal lines (and the bottom of
the plot) represent approximate limiting magnitudes for the various
types of observations proposed: V=16-17 for MIRSI, 17.5 for VLT AO
satellite searches, 18 for low-res. SpeX (current), and 19.5 for
improved TCS SpeX; our nominal limits are 17.5 and 19.5 for
lightcurve photometry and 18 for Keck spectra. Visibility is
assumed when the target has elevation >25 deg. and >15 deg.
from the Moon. Ticks on the horizontal axis indicate years and
months. There are several oppositions for some targets during the
3.5 years displayed. Such plots and tools we have developed are
useful in planning telescope proposals in order to efficiently
observe as many targets as possible.
Fig. 8 from NASA PAST proposal (where it is called Fig. 7)
Fig. 8. Shown here is a pair of spectra taken recently by Co‑I
Young with NIRSPEC at R=2200. These spectra of the Centaur Chariklo
(Vmag = 17.79) were obtained in 2 consecutive 5‑minute exposures at
2 different slit positions ("A" and "B"). We show the A‑minus‑B
pair here. The counts in either beam were ~170 DN above the
background in 300 sec., or ~6 times the average background of 27
DN.
***Need 1-page summary sheet, mentioning both
intellectual/technical and broader merits, 3d person
***Need my 2-pg bio sketch (w collaborators)
***Things to be taken care of Friday:
Check for failure to convert special symbols (e.g. diacritical
marks in Knezevic’s name [2nd parag of Tech Background], symbols
dealing with proper elements, etc.)
Alisha should try to format tables the way she did for NASA
proposal.
Alisha could also try to save space by reducing the spaces
between paragraphs from a full extra line space to perhaps half an
extra line space. I’ve spent half an hour trying, unsuccessfully to
figure out Bill Gates silly line-spacing/paragraph spacing
controls.
There are specifications for margins, lines per inch, font-size,
etc. I think I have these approximately set, but there may remain
issues (with the page no. footers, for example). We may have to
compromise slightly, and I have done so in selection of fonts for
captions, line spacings within tables, etc. In particular, the
margin on pg. 1 is too narrow because I don’t know how to handle
footers.
Eliot failed in his promise to get back to me last night about
the limits for MIRSI. If the current V=16-17 is woefully wrong,
Bill & Eliot could try to change these. Also, I found that
Eliot had failed to check some absurdly obsolete statements about
himself…I fear that Eliot’s checking of stuff is inadequate, and we
are “winging it” on his stuff for the third year in a row. If
something can be done to double-check this stuff, it really should
be.
I have the figures and captions at the end of the text. They
should be moved up to within a page-or-so of where they are first
mentioned. Some of the figures are not available to me. They must
be obtained from the NASA Planetary Astronomy proposal. I will try
to check late today that the figures have been inserted
correctly.
David and others should check that the captions (especially for
new figures) are correct. I found that they hadn’t been changed
when the new figures were made.
The references should be separated from the text and placed
where required. It would be nice if someone could verify that there
are no old “submitted” or “in press”.
Alisha – Bill evidently can’t read Word documents. Please print
a copy for him.
Alisha – double-ck that the page of budget explanations
referenced in the final paragraph of Sec. V in fact exsits where we
say it does.
OK to shrink figures somewhat more (so long as still legible) to
gain space.